By-vdev: why is it called that?

The vdev_id.conf file can be used to create entries with convenient channel names in /dev/disk/by-vdev with udev. My question is: why is it called “by-vdev”? This seems to overlap in meaning with a zpool vdev (virtual device, consisting of a set of physical drives), yet it seems to be a very different meaning (normally referring to individual disks). Surely, they could have used “by-udev”? Or another term not already in use within ZFS terminology?

I figured understanding the motivations behind the naming would help prevent confusion.